Friday, 30 June 2017

M11: The Wild Duck Cluster

I've already written about this object here, but it definitely deserves a more detailed blog post, so here we go. The 11th object on Messier's list, also referred to as the "Wild Duck Cluster", is one of the richest star clusters in our Milky Way. Its rather odd nickname was invented by Admiral Smyth in the 19th century, who saw a sort of V-shape in it, just like a flock of wild ducks. It contains some 2,900 stars, 500 of which are brighter than mag. 14, and various dark lanes which seem to divide the cluster. In spite of its considerable distance (6,100 light-years), it is one of summer's grandest objects and can already be spotted quite easily with ordinary binoculars in the inconspicuous constellation of Scutum, the shield. It's so amazingly compact that at low power it might be mistaken for a globular cluster. Increasing telescope power will reveal its true nature as a cluster of newborn stars. Being some 250 million years old, this cluster's middle-aged but considering its size and compactness there's no doubt that it will continue to resist our galaxy's gravitational pull for millions of years to come. Yet, some of the most massive stars in it have already evolved into red giant phase, meaning that they've depleted their hydrogen and are now fusing helium into heavier elements. As I've already explained, the bigger a star, the faster it will burn its hydrogen and the shorter it will live.

The brightest star, right at the cluster's centre however... isn't a member at all. It lies 1,300 light-years closer to us! So once again you see that astronomical observations can be deceiving.